Michael Crichton's latest novel, State of Fear, is an action-packed thriller in which the hero is a scientist who discovers that climate change is all a fraud. The novel has sold well, but it was still something of a shock yesterday to find its author as an expert witness testifying on global warming in front of the United States Senate.

Crichton had been summoned to give evidence by Senator James Inhofe, a Republican senator from Oklahoma, who recently called global warming "the greatest hoax ever perpetrated on the American people".

Some scientists speculated that Crichton might be the best witness Senator Inhofe could find. A 2004 survey of 900 peer-reviewed and published scientific papers on climate change failed to find a single one who went against the belief that man-made change is happening and is dangerous.

But it was hard to imagine a more star-struck audience than the line-up of Republican senators who rushed to shake the author by the hand yesterday as he arrived in the oak-panelled committee room on Capitol Hill. "I've never seen this before," said one old hand of the Washington press corps. "Usually, they barely give the witnesses a second glance."

"I would like to thank Dr Crichton for the endless hours of entertainment he has given me on Delta Airlines," began one senator. "Dr Crichton's science background has served him well in providing material for his books, many of which explore scientific issues, my favourite of which is State of Fear," gushed Sen Inhofe, chairman of the committee. "I urge you all to read this book."

Crichton has aged considerably since the photograph that adorns the back of his latest novel was taken. The face is more lined, and the slicked back jet-black hair is shorter and greying at the edges, with a distinct bald spot on the back of his head. But none of that could take away from the fact that, standing at least 6ft 7in tall, he was a towering presence at the witness table.

"I am Michael Crichton, known to most people as the author of Jurassic Park and the creator of the television series ER," he began. "My academic background includes degrees from Harvard College and Harvard Medical School; I was a visiting lecturer in Physical Anthropology at Cambridge University, and a postdoctoral fellow at the Salk Institute, where I worked on media and science policy."

He continued: "My recent novel, State of Fear, concerns the politicisation of scientific research ... What I would like to emphasise to the committee today is the importance of the independent verification to science."

What followed was a detailed critique of one of the major studies into climate change, carried out by the American climate researcher Michael Mann in the late 1990s, effectively accusing the scientists of failing to adhere to proper scientific standards.

Drawing on what he said was experience from his medical background, he told the assembled senators that any study where a single team plans the research, carries it out, supervises the analysis, and writes their own final report carries a "very high risk " of undetected bias.

But despite his critique of what is commonly regarded to be one of the first - and most important - studies on the history of global warming, he said it was not his intention to debunk the theory of global warming.

"In closing, I want to state emphatically that nothing in my remarks should be taken to imply that we can ignore our environment, or that we should not take climate change seriously. On the contrary, we must dramatically improve our record on environmental management. That's why a focused effort on climate science, aimed at securing sound, independently verified answers to policy questions, is so important now."

Not all senators were uniformly impressed. Hillary Clinton was the first to try to cut him down to size. "His views on climate change are at odds with the vast majority of climate scientists; it also appears in a work of fiction," the senator for New York said dismissively. "I think that the topic of this hearing is very important but organised in a way to muddy sound science rather than clarify it," she added, before thanking the other four witnesses who attended, but not Crichton.

Democratic Senator Barbara Boxer joined in. "We are here to talk about sound science - a worthy and important subject. We are not here to talk about plays, novels, art or music - although as a member for California I do appreciate the focus on the arts."

"A lot of people are being maligned here, I take great offence at that, they are not here and they are being maligned," she said, asking if she could put on record a letter from one of the aforementioned maligned scientists.

By the time Crichton and the other four panellists had finished their opening statements, most of the senators, including Mrs Clinton, had left to attend another Senate hearing on the ramifications of Hurricane Katrina.

Outside the committee room, Peter Saundry, executive director of the National Council for Science and the Environment, said he was bemused by Crichton's apparent position. "If you read his book, you are left with the impression that environmentalists are only one step up from the sort of people who will cross the road to murder your children, but then you get to the author's note at the back and he makes this statement saying he is not a climate change denier. It's hard to know what his position is."